C#

protected override CreateParams CreateParams 
{
   get
   {
      System.Windows.Forms.CreateParams param = base.CreateParams;
      //we need to prevent to control calling the vscroll or hscroll
      //vscroll
      if ((0x00200000 & param.Style) != 0)
      {
         param.Style -= 0x00200000;
      }
      //hscroll
      if ((0x00100000 & param.Style) != 0)
      {
         param.Style -= 0x00100000;
      }
      return param;
   }
}

using System.Diagnostics;
...
protected override void OnClosing(CancelEventArgs e) 
{
    base.OnClosing(e);
    
    StackTrace t = new StackTrace(false);
    
    // NB: If you override, you need frame 6.
    // If you handle the event, you need frame 7.
    StackFrame f = t.GetFrame(6);
    
    switch (f.GetMethod().Name) 
    {
        case "CallWindowProc":
            // System menu, or the close button
        case "DefMDIChildProc":
            // MDI Child System Menu or close button
        case "DefFrameProc":
            // MDI Parent Closing
        case "ShowDialog":
            // Modal Dialog Closing
        case "DispatchMessageW":
        case "DispatchMessageA":
            // Task manager
        case "SendMessage":
            // Call in code
        default:
            //Don't know
            break;
    }
}